1. Field of the Invention
The present invention relates to an electronic musical instrument and more particularly to a panning control apparatus for an electronic musical instrument.
2. Description of the Prior Art
A panning control apparatus has been known which moves a sound image formed by musical tones output in a stereophonic fashion by changing the sound-volume balance the left and right channel musical tones (U.S. Pat. No. 4,577,540).
Further, a panning control apparatus with an automatic panning function has been well known which cyclically moves the above sound image by periodically changing sound-volume balance of musical tones (U.S. Pat. No. 4,648,115).
However, a single panning effect is applied to all of the musical tone during a performance in these known apparatuses. Therefore, there is a limitation in expression of the sound-field effect in the conventional techniques.
Recently, a Musical Instrument Digital Interface (MIDI) system has been proposed as a communication interface which serves for communication between electronic musical instruments (including sequencers, sound modules and the like). Generally, this kind of communication interface has a conception of communication channels. Sixteen communication channels are prepared for a MIDI system. A message on each MIDI channel serves basically as performance data related to one unit of "musical instrument". Upon recent demands for variations in musical-tone expression, one communication system has been put to practical use, which has a mode (so called a combination mode), where, a receiving side (a slave having a sound source) generates a plurality of groups of musical tones by fixedly assigning the musical tones to sound modules of the sound source with a single sound-generation message (note-on/note-off information) supplied from a MIDI channel, or by changing the assignment fashion according to the information (note number representing a tone pitch, velocity indicating touch) included in the sound-generation message. For instance, in a tone-mix mode (one of combination mode), more than one musical tone (musical tones having different tone colors or having different relative pitches) is fixedly assigned to one sound-generation message, and whereby are obtained a similar effect to that of a unison performance executed with a plurality of "musical instruments" having different tone colors, a similar effect to that of a performance executed with a single "musical instrument" having an affluent tone color or a profound acoustic effect generated with a plurality of musical instruments of the same groups, which generate musical tones having the same tone color but having different pitches by one octave or pitches detuned a little, or which generate musical tones with a little time delay. Further in the combination mode called--key-split--, tone colors of musical tone corresponding to the sound-generation message can be selectively changed in accordance with tone areas. For example, when a keyboard musical instrument is used as a MIDI controller, effects of a performance executed with a musical instrument having a certain tone color assigned to a left-hand operating area and effects of a performance executed with a musical instrument having another tone color assigned to a right-hand operating area (effects of a performance executed by two groups of musical instruments) are available. Further, there have been proposed a combination mode in which tone color can be continuously changed on the basis of tone areas, a combination mode in which tone color is changed by a touching operation during performance and a combination mode such as a composite, mode composed of a tone-mix mode and the key split made.
However, the present technical level only allows to execute the panning control of the same manner on a plurality of groups of musical tones assigned to one communication channel on the basis of data supplied from one manipulator (manipulator data supplied through one communication channel).
The function of the combination mode itself is independent of the MIDI system. Though an electronic musical instrument is also known, in which a plurality of groups of musical tones can be assigned to a sound-generation message generated in the musical instrument, this type of electronic musical instrument still has a drawback that the panning effect is applied to all the groups of musical tones in a similar way by a single manipulator.
As described above, the panning control apparatus is known which is capable of controlling by means of the manipulator the location of a sound image formed by musical tones output in a stereophonic fashion. Further, a panning control apparatus has been proposed which is capable of switching the manipulators providing the panning effect. In addition, there is variety in mechanical constructions of the manipulator. However, in the conventional technique, the relationship between the manipulator data and the sound-image location is kept constant in the process to be executed after manipulator-digital data has been once detected in accordance with input data from the manipulator. For instance, in the MIDI system, manipulator data takes values from "0" to "127" and the values of data are fixedly defined as follows: the value "0" indicates that the sound image located at a position of the left speaker and the value "127" indicates that the sound image is located at a position of the right speaker (in a two-channel stereophonic system). Therefore, there is a limitation to the dynamism of the sound image to be practically controlled by the manipulator.